Aluminum alloy electrical conductor

ABSTRACT

Aluminum alloy electrical conductors are produced from aluminum base alloys containing from about 0.20 to about 1.60 weight percent cobalt, from about 0.30 to about 1.30 weight percent iron, up to about 0.40 weight percent magnesium, up to about 0.40 weight percent copper, from about 99.50 to about 97.00 weight percent aluminum and up to about 0.45 weight percent each of additional alloying elements, the total weight percent of additional alloying elements not exceeding about 0.70 percent; the total weight percent of magnesium and copper not exceeding about 0.40 percent and the total weight percent of additional alloying elements not exceeding about 0.40 percent when the total weight percent of cobalt and iron exceeds about 1,80 percent. The alloy conductors have an electrical conductivity of at least 57 percent, based on the International Annealed Copper Standard (IACS), and improved properties of increased thermal stability, tensile strength, percent ultimate elongation, ductility, fatigue resistance and yield strength as compared to conventional aluminum alloys of similar electrical properties.

United States Patent 1191 Schoerner et al.

1 ALUMINUM ALLOY ELECTRICAL CONDUCTOR [75] Inventors: Roger J.Schoerner; Enrique C.

- Chia, both of Carrollton, Ga.

[73] Assignee: Southwire Company, Carrollton,

[22] Filed: June 5, 1972 [21] Appl. No.: 259,722

Related U.S..Applicati0n Data [63] Continuation-in-part of Ser. No.94,193, Dec. 1, 1970, abandoned, which is a continuation-in-part of Ser.No. 54,563, July 13, 1970, abandoned.

[52] US. Cl 29/193, 29/527.7, 75/138, 75/143, 148/2, 148/32, 164/76 [51]Int. Cl B2lc 1/00, C22f 1/04 [58] Field of Search 29/183, 183.5, 193,527.7; 75/138-148; 148/2, 3, 11.5 A, 32; 164/76 [56] References CitedUNITED STATES PATENTS 1,579,481 4/1926 Hybinette 75/138 1,932,79510/1933 McCullough 75/142 1,932,838 10/1933 Dean et al. 75/147 1,945,2971/1934 Sterner-Rainer 75/147 3,160,513 12/1964 Westerveld et al. 75/1383,670,401 6/1972 Schoerner 148/2 FOREIGN PATENTS OR APPLICATIONS 498,2271/1939 Great Britain 706,721 6/1931 France OTHER PUBLICATIONS Kruptokinet al., The Mechanical Properties of AVOOO Aluminum with Small Additionsof Different 1 51 May 21, 1974 Elements, Metals Abstract, December,2,291.

Kruptokin, Influence of Small Additions of Iron, Nickel and Cobalt onMechanical Properties and Conductivity of Aluminum, Slavic Library,November 30, 1965, Battell Memorial Institute.

Primary ExaminerRichard 0. Dean Attorney, Agent, or FirmHerbert M.Hanegan; Van C. Wilks 5 7 ABSTRACT Aluminum alloy electrical conductorsare produced from aluminum base alloys containing from about 0.20 toabout 1.60 weight percent cobalt, from about 0.30 to about 1.30 weightpercent iron, up to about 0.40 weight percent magnesium, up to about0.40 weight percent copper, from about 99.50 to about 97.00 weightpercent aluminum and up to about 0.45 weight percent each of additionalalloying elements,

, the total weight percent of additional alloying ele- 32 Claims, N0Drawings l ALUMINUM ALLOY ELECTRICAL CONDUCTOR CROSS-REFERENCE TORELATED APPLICATION This application is a continuation-in-part of ourcopending application, Ser. No. 94,193, filed Dec. 1,

1970, now abandoned, which in turn is a continuation-- in-part of ourcopending application, Ser. No. 54,563, filed July 13, 1970, nowabandoned.

The present invention concerns an aluminum base alloy especially suitedfor producing high strength lightin the marketplace of today because oftheir light weight and low cost. One area where aluminum alloys havefound increasing acceptance is in the replacement of copper in themanufacture of electrically conductive wire. Conventional electricallyconductive aluminum alloy wire(referred toas EC) contains a substantialamount of pure aluminum and trace amounts of impurities such as silicon,vanadium, iron, copper, manganese, magnesium, zinc, boron, and titanium.

Even though desirable in terms of'weight andcost, aluminum' alloys havereceived far less than complete acceptance in the electrical conductormarketplace. One of the chief reasons for the lack of completeacceptance is the range of physical properties available withconventional EC aluminum alloy conductors. If the physical properties,such as thermal stability, tensile strength, percent elongation,ductility and yield strength,could be improved significantly withoutsubstantially lessening. the electrical conductivity of the finishedproduct, a very desirable improvement would be achieved. lt is accepted,however, that addition of alloying elements, as in other aluminumalloys, reduces conductivity while improving the physical properties.Consequently, only those additions of elements which improve physicalproperties without substantially lessening conductivity will yield anacceptable and useful product.

It is an object of the present invention, therefore, to provide a newaluminum alloy electricalconductor which combines improved physicalproperties with acceptable electrical conductivity. These and otherobjects, features and advantages of the present invention will beapparent from a consideration of the following detailed-description ofan embodiment of the invention.

In accordance with the invention, the present aluminum base alloy isprepared by mixing cobalt, iron and optionally other alloyingelernentswith aluminum in a furnace to obtain a melt having requisite percentagesof elements. lt has been found that suitable results are obtainedwithcob'alt present in a weight percentage of from about 0.20 percent toabout 1.60 percent. Superior results are achieved when cobaltis presentin a weight percentage of from about 0.20 percent to about 1.00 percentand particularly superior and preferred results are obtained when cobaltis presentin a percentage by weightof from about 0.30 percent to about0.80

percent. 7

Suitable results are obtained with iron present in a weight percentageof from about 0.30 percent to about 1.30 percent. Superior results areachieved when iron is present in a weight percentage of from about 0.30percent to about 1.00 percent and particularly superior and preferredresults are obtained when iron is present in a percentage by weight offrom about 0.40 percen to about 0.70 percent.

The aluminum content of the present alloy may vary from about 97.00percent to about 99.50 percent by weight with superior results beingobtained when the aluminum content varies between about 97.90 percentand about 99.50 percent by weight particularly superior and preferredresults are obtained when aluminum is present in a percentage by weightof from about 98.40 percent to about 99.30 percent. Since thepercentages for maximum and minimum aluminum do not correspond with themaximums and minimums for alloyingelements, it should be apparent thatsuitable results are not obtained if the maximum percentages for allalloying elements are employed. If commercial aluminum is employed inpreparing the present melt, it is preferred that the aluminum, prior toadding to the melt in the furnace, contain no more than 0.10 percenttotal of trace impurities.

Copper and magnesium'have a high solubility in aluminum at roomtemperature, consequently the electrical conductivity is decreased dueto the known effect of atoms in solid solution on the electricalconductivity of aluminum. The present alloy may contain up to about 0.40weight percent copper and up to about 0.40 weight percent magnesium.

The present alloy may contain up to about 0.45 percent by weight each ofadditional alloying elements, the total weight percent of additionalalloying elements not exceeding about 0.70 percent. Superior results areobtained when the concentration of individual optional alloying elementsis about 0.30 percent by weight or less and the total additionalalloying elements not exceeding about0.60 weight percent. Particularlysuperior and preferred results are obtained when the concentration ofindividual optional alloying elements is about 0.20 percent by weight orless and the total additional alloying elements not exceeding about 0.40weight percent.

Additional alloying elements include the following:

Superior results are obtained with the following additional alloyingelements in the percentages, by weight, as shown:

PREFERRED ADDlTlONAL ALLOYING ELEMENTS Nickel 0.0005% to 0.45% Silicon0.001% to 0.45% Zirconium 0.00l% to 0.45% Niobium 0.00l% to 0.45%Tantalum 0.00l% to 0.45% Yttrium 0.00l% to 0.45%

-Continued PREFERRED ADDlTlONAL ALLOYlNG ELEMENTS Mixtures of two ormore of the above 0.001% to 0.70

Particularly superior and preferred results are obtained with the use ofsilicon in a percentage range of from about 0.001 to about 0.45 percentby weight, additional alloying elements in a percentage range of fromabout 0.0005 to about 0.25 percent by weight, and nickel or magnesium asadditional alloying elements. Suitable results are obtained withmagnesium or nickel in a percentage range of from about 0.0005 to about0.40 percent by weight. Superior results are obtained with from about0.025 to about 0.30 percent by weight magnesium or nickel, silicon in apercentage range of from about 0.001 to about 0.30 percent by weight,and from about 0.0005 to about 0.25 percent by weight additionalalloying elements. Particularly superior and preferred results areobtained when from about 0.03 to about 0.10 percent by weight ofmagnesium or nickel is employed with from about 0.001 to about 0.20percent by weight silicon and from about 0.0005 to about 0.20 weightpercent additional alloying elements.

Superior and preferred results are also obtained with the use of cobaltand iron in the percentage ranges previously specified with additionalalloying elements and optionally with silicon as the major additionalalloying elements.

Suitable results are obtained with the use of silicon as the majoradditional alloying element in a percentage range of from about 0.001 toabout 0.45 percent by weight and from about 0.0005 to about 0.25weightpercent additional alloying elements with superior results beingobtained with from about 0.001 to about 0.30 weight percent silicon andfrom about 0.0005 to about 0.25 weight percent additional alloyingelements. Particular superior and preferred results are obtained withfrom about 0.001 to about 0.20 weight percent silicon and from about0.0005 to about 0.10 weight percent additional alloying elements.

When silicon is not the major additional alloying element suitableresults are obtained with the use of cobalt and iron in the percentageranges previously specified and from about 0.0005 to about 0.70 weightpercent additional alloying elements. Superior results are obtained withfrom about 00005 to 0.60 weight percent additional alloying elementswith particular superior and preferred results obtained with from about0.0005 to about 0.40 weight percent additional alloying elements.

The rare earth metals may be present either individually within thepercentage range stated or as a partial or total group, the totalpercentage of the group being within the percentage range statedpreviously.

It should be understood that the additional alloying elements may bepresent either individually or as a group of two or more of theelements. It should be understood, however, that if two or more of theadditional alloying elements are employed, the total concentration ofadditional alloying elements should not exceed about 0.70 percent byweight.

When the total weight percent of cobalt and iron exceeds about 1.80percent the total weight percent of magnesium and copper should notexceed about 0.40 percent and the total weight percent of additionalalloying elements should not exceed about 0.40 percent in order tomaintain the desired electrical conductivity and physical properties.

If the total weight percent cobalt and iron is about 2.90 percent thetotal weight percent of magnesium and copper should not exceed about0.20 percent and the total weight percent of additional alloyingelements should not exceed about 0.10 percent.

After preparing the melt, the aluminum alloy is preferably continuouslycast into a continuous bar by a continuous casting machine and thensubstantially immediately thereafter, hot-worked in a rolling mill toyield a continuous aluminum alloy rod.

One example of a continuous casting and rolling operation capable ofproducing continuous rod as specified in this application is containedin the following paragraphs. It should be understood that other methodsof preparation may be employed to obtain suitable results but thatpreferable results are obtained with continuous processing. Such othermethods include conventional extrusion and hydrostatic extrusion toobtain rod or wire directly, sintering an aluminum alloy powder toobtain rod or wire directly, casting rod or wire directly from a moltenaluminum alloy, and conventional casting of aluminum alloy billets whichare subsequently hot-worked to rod and drawn with intermediate annealsinto wire.

CONTINUOUS CASTING AND ROLLING OPERATION A continuous casting machineserves as a means for solidifying the molten aluminum alloy metal toprovide a cast bar that is conveyed in substantially the condition inwhich it solidified from the continuous casting machine to the rollingmill, which serves as a means for hot-forming the cast bar into rod oranother hotformed product in a manner which imparts substantial movementto the cast bar along a plurality of angularly disposed axes.

The continuous casting machine is of conventional casting wheel typehaving a casting wheel with a casting groove in its periphery which ispartially closed by an endless belt supported by the casting wheel andan idler pulley. The casting wheel and the endless belt cooperate toprovide a mold into one end of which the cast bar is emitted insubstantially that condition in which it solidified.

The rolling mill is of conventional type having a plurality of rollstands arranged to hot-form the cast bar by a series of deformations.The continuous casting machine and the rolling mill are positionedrelative to each other so that the cast bar enters the rolling millsubstantially immediately after solidification and in substantially thatcondition in which it solidified. In this condition, the cast bar is ata hot-forming temperature within the range of temperatures forhot-forming the cast bar at the initiation of hot-forming withoutheating between the casting machine and the rolling mill. In the eventthat it is desired to closely control the hotforrning temperature of thecast bar within the conventional range of hot-forming temperatures,means for adjusting the temperature of the cast bar may be placedbetween the continuous casting machine and the rolling mill withoutdeparting from the inventive concept disclosed herein.

The roll stands each include a plurality of rolls which engage the castbar. The rolls of each roll stand may be two or more in number andarranged diametrically opposite from one another or arranged at equallyspaced positions about the axis of movement of the cast bar through therolling mill. The rolls of each roll stand of the rolling mill arerotated at a predetermined speed by a power means such as one or moreelectric motors and the casting wheel is rotated at a speed generallydetermined by its operating characteristics. The rolling mill serves tohot-form the cast bar into a rod of a crosssectional area substantiallyless than that of the cast bar as it enters the rolling mill.

The peripheral surfaces of the rolls of adjacent roll stands in therolling mill change in configuration; that is, the cast bar is engagedby the rolls of successive roll stands with surfaces of varyingconfiguration, and from different directions. This varying surfaceengagement of the cast bar in the roll stands functions to knead orshape the metal in the cast bar in such a manner that it is worked ateach roll stand and also to simultaneously reduce and change thecross-sectional area of the cast bar into that ofthe rod.

As each roll stand engages the cast bar, it is desirable that the castbar be received with sufficient volume per unit of time at the rollstand for. the cast bar to generally fill the space defined by the rollsof the roll stand so that the rolls will'be effective to work the metalin the cast bar. However, it is also desirable that the space defined bythe rolls of each roll stand not be overfilled so that the cast bar willnot be forced into the gaps between the rolls. Thus, it is desirablethat the rod be fed toward each roll stand at a volume per unit of timewhich is sufficient to fill, but not over fill, the space defined by therolls of the roll stand.

As the cast bar is received from the continuous casting machine, itusuallyhas one large flat surface corresponding to the surface of theendless band and inwardly tapered side surfaces corresponding to theshaped the groove in the casting wheel. As the cast bar is compressed bythe rolls of the roll stands, the cast bar is deformed so that itgenerally takes the crosssectional shape defined by the adjacentperipheries of the rolls of each roll stand.

Thus, it will be understood that with this apparatus, cast aluminumalloy rod of an infinite number of different lengths is prepared bysimultaneous casting of the molten aluminum alloy and hot-forming orrolling the cast aluminum bar. The continuous rod has a minimumelectrical conductivity of 57 percent IACS and may be used in conductingelectricity or it may be drawn to wire of a smaller cross-sectionaldiameter.

To produce wire of various gauge, the continuous rod produced by thecasting and rolling operation is processed in a reduction operation. Theunannealed rod (i.e., as rolled to f temper) is cold-drawn through aseries of progressively constricted dies, without interme diate anneals,to form a continuous wire of desired diameter. lt has been found thatthe elimination of intermediate anneals is preferable during theprocessing of the rod and improves the physical properties of the wire.Processing with intermediate anneals is acceptable when the requirementsfor physical properties of the wire permit reduced values. Theconductivity of the hard-drawn wire is at least 58 percent IACS. Ifgreater conductivity or increased elongation is desired, the wire may beannealed or partially annealed after the desired wire size is obtainedand cooled. Fully annealed wire has a conductivity of at least 59percent IACS. At the conclusion of the drawing operation and optionalannealing operation, itis found that the alloy wire has the propertiesof improved tensile strength and yield strength together with improvedthermal stability, percent ultimate elongation and increased ductilityand fatigue resistance as specified previously in this application. Theannealing operation may be continuous as in resistance annealing,induction annealing, convection annealing by continuous furnaces .orradiation annealing by continuous furnaces, or, preferably, may be batchannealed in a batch furnace. When continuously annealing, temperaturesof about 450F to about l,200F may be employed with annealing times ofabout 5 minutes to about U 10,000 of a minute. Generally, however,continuous annealing temperatures and times may be adjusted to meet therequirements of the particular overall processing operation so long asthe desired physical properties are achieved. In a batch annealingoperation, a temperature of approximately 400F to about 750F is employedwith residence times of about 30 minutes to about 24 hours. As mentionedwith respect to continuous annealing, in batch annealing the times andtemperatures may be varied to suit the overall process so long as thedesired physical properties are obtained.

It has been found that the properties of a Number 10 gauge (Americanwire gauge) fully annealed soft wire of the present alloy vary betweenthe following figures:

A more complete understanding of the invention will be obtained from thefollowing examples.

EXAMPLE NO. 1

Various melts are prepared by adding the required amount ofalloying'elements to 1,816 grams of molten aluminum, containing lessthat 0.1 percent trace element impurities, to achieve a percentageconcentration of elements as shown in the accompanying table; theremainder being aluminum. Graphite crucibles are used except in thosecases where the alloying elements are known carbide formers, in whichcases aluminum oxide crucibles are used. The melts are held forsufficient times and at sufficient temperatures to allow completesolubility of the alloying elements with the base aluminum. An argonatmosphere is provided over the melt to prevent oxidation. Each melt iscontinuously cast on a continuous casting machine and immediatelyhot-rolled through a rolling mill to inch continuous rod. Wire is thendrawn from the rod in both the asrolled condition (hard rod) and afterbeing annealed for 5 hours at 650F (soft rod). The final wire diameterobtained is 0.107 inches, 10 gauge AWG. Wire from each type rod istested in both the as-drawn condition (hard wire) and after beingannealed for 5 hours at 650F (soft wire).

The types of alloys employed and the results of the tests performedthereon are as follows:

TABLE 1 Co Fe Mg Ni HR SR HW-HR HW-SR SW-HR SW-SR Properties .80 .80 .082.1 25.5 2.0 2.5 17.8 24.5 7: Elong.

31.450 19.400 38.040 34.045 19.790 18.978 UTS 58.38 59.63 58.03 58.7959.76 59.98 70 IACS .80 .80 4.3 22.0 3.0 3.0 21.0 22.0 70 Elong.

27.800 18.340 31.700 27.450 17.590 15.750 UTS 59.01 61.42 58.37 59.8860.48 60.63 [AC 1.0 .80 3.3 20.1 4.2 2.3 25.0 27.7 Elong.

28.150 17.875 32.135 26.685 17.200 16.275 UTS 58.38 59.90 58.37 59.2959.86 60.06 lACS .80 .80 .10 1.1 14.5 3.4 2.0 20.5 24.5 Elong.

34.395 19,650 40.360 36.700 20.280 19,240 UTS 57.56 59.38 56.80 58.0759.02 59.33 lACS .40 .80 .10 .40 2.8 20.0 2.0 2.5 22.9 24.5 Elong.

30.340 17.110 37.935 32.500 18,350 17,245 UTS 59.19 60.65 58.64 59.6660.65 60.72 lACS HR Hard Ro SW-SR Soft Wire drawn from Soft Rod SR SoftRod Elong. Percent ultimate elongation HW-HR Hard Wire drawn from HardRod UTS Ultimate Tensile Strength HW-SR Hard Wire drawn from Soft RodlACS Conductivity in Percentage lACS SW-HR Soft Wire drawn from Hard RodSoft wire and soft rod are the fully annealed forms of the products.

EXAMPLE NO. 2

An additional alloy melt is prepared according to Example No. 1 so thatthe composition is as follows in weight percent:

Cobalt 0.60%

lron 0.90% Magnesium 0.15% Aluminum Remainder The melt is processed to aNo. 10 gauge soft wire from hard rod. The physical properties of thewire are as fol lows:

Ultimate Tensile Strength 20.040 psi Percent Ultimate Elongation 18.50%Conductivity 59.05% lACS EXAMPLE NO. 3

An additional alloy melt is prepared according to Example No. 1 so thatthe composition is as follows in weight percent:

Cobalt 0.80%

lron 0.50% Misch Metal 0.40% Aluminum Remainder Ultimate TensileStrength 18,500 psi Percent Ultimate Elongation 19% Conductivity 59.2%lACS EXAMPLE NO. 4

An additional alloy melt is prepared according to Example No. 1 so thatthe composition is as follows in weight percent:

Cobalt 0.80? lron 0.40"- Niohium 0.20% Tantalum 0.20% Aluminum RemainderThe melt is processed to a No. 10 gauge soft wire from hard rod. Thephysical properties of the wire are as follows:

Ultimate Tensile Strength 19.380 psi Percent Ultimate Elongation 19.5%Conductivity 59.171 lACS EXAMPLE NO. 5

An additional alloy melt is prepared according to Example No. 1 so thatthe composition is as follows in weight percent:

Cobalt 0.80% Iron 0.35% Copper 0.40% Silicon 0.30% Aluminum RemainderThe melt is processed to a No. 10 gauge soft wire from hard rod. Thephysical properties of the wire are as follows:

Ultimate Tensile Strength 17,000 psi Percent Ultimatc Elongation 19.5%Conductivity 59.7% lACS EXAMPLE NO. 6

An additional alloy melt is prepared according to Example No. 1 so thatthe composition is as follows in weight percent:

Cobalt 0.80% lron 0.45% Zirconium 0.30% Aluminum Remainder The melt isprocessed to a No. 10 gauge soft wire from hard rod. The physicalproperties of the wire are as follows: I

Ultimate Tensile Strength 18,600 psi Percent Ultimate Elongation 18.5%Conductivity 59.3% lACS ADDITIONAL EXAMPLES I Additional alloy melts areprepared according to Example No. l. The composition and the physicalproperand a majority are less than 2 microns in length and less thanone-half micron in width.

The iron aluminate intermetallic compound also contributes to thepinning of dislocation sites during cold ties of a 10 gauge ft Wireffom'hafll rod of the 5 working of the wire. Upon examination of theiron inalloy melts are as follows:

termetallic compound precipitate in a cold drawn wire,

TABLE 2 Example UTS lACS 0. Co Fe Mg in psi Elongation Conductivity 1176.8 .5 17,430 24.7 60.68 1177 .8 .5 1 17,410 24.8 60.43 1183 .8 .3 17,78526.6 61.65 11114 .8 .5 17,700 28.0 61.54 1185 .6 .9 18,485 23.7 60.761186 .8 .9 17,930 26.5 59.97 1187 .4 1.1 19,355 19.8 60.19 11811 .6 1.120,400 17.5 59.87 1196 .2 1.1 18,515 20.5 60.41 1 I97 .4 .9 I 17,49522.4 60.40 1198 .4 1.1 18,695 21.5 60.02 1199 .6 .9 18,975 20.3 60.991200 .2 .7 .1 17,775 22.8 60.83 1216 .8 Graphite .05 17,635 27.3 61.84

. .01 1219 .8 .53 17,180 29.2 61.62 1220 .8 .4 17 ,480 29.0 61.31 1221.8 .5 .051 18,965 26.4 61.28 1227 .8 .5 .05 18,785 17.1 60.72 1228 .8 .5.2 17,140 27.2 60.56 1237 .7 .5 17,030 24.5 61.49 1238 .8 .7 17,295 26.460.96 1239 .6 .5 .05 17,975 22.7 61.29 1201 .6 .9 .1 20,898 20.7 59.151240 .8 .3 .05 17,630 23.3 61.25 1293 1.40 .49 17,120 24.5 59.52 1313.20 1.10 12 17,400 24.2 60.01 1316 .22 .96 .15 17,425 22.0 59.92 1317.23 1.20 .14 18.333 23.7 59.47 1321 .43 .70 .054 17,200 26.5 61.12 1322.40 1.05 .05 17,830 22.0 60.12 1325 .40 .68 .10 17.792 25.5 60.44 1327.38 1.10 .11 19,004 25.2 59.52 1328 .42 .35 .15 17,000 24.0 60.88 1329.41 .50 .16 17,000 24.0 60.47 1330 .44 .70 .16 18,100 25.0 59.80 1331.42 .91 .16 18,690 22.0 60.51 1343 .33 .95 M54 20,874 16.4 49.90 1.0HF

Through testing and analysis of an alloy containing 0.80 weight percentcobalt, 0.30 weight percent iron, and the remainder aluminum, it hasbeen found that the present aluminum base alloy after cold workingincludes intermetallic compound precipitates. One of the compounds isidentified as cobalt aluminate (Co A1 and the other is identified asiron aluminate (FeAl The cobalt intermetallic compound is found to bevery stable and especially so at high temperatures. The cobalt compoundalso has a low tendency to coalesce during annealing of products formedfrom the alloy and the compound is generally incoherent with thealuminum matrix. The mechanism of strengthening for this alloy is inpart due to the dispersion of the cobalt intermetallic compound as aprecipitate throughout the aluminum matrix. The precipitate tends to pindislocation sites which are created during cold working of the wireformed from the alloy. Upon examination of the cobalt intermetalliccompound precipitate in a cold drawn wire, it is found that theprecipitates are oriented in the direction of drawing. In addition, itis found that the precipitates are rod-like or plate-like inconfiguration it is found that the precipitates are substantially evenlydistributed through the alloy and have a particle size of less than 1micron. If the wire is drawn without any intermediate anneals, theparticle size of the iron intermetallic compounds is less than 2,000angstroms.

A characteristic of high conductivity aluminum alloy wires which is notindicated by the historical tests for tensile strength, percentelongation and electrical conductivity is the possible change inproperties as a result of increases, decreases or fluctuations of thetemperature of the strands. It is apparent that the maximum operatingtemperature of a strand or series of strands will be affected by thistemperature characteristic. The characteristic is also quite significantfrom a manufacturing viewpoint since many insulation processes requirehigh temperature thermal cures.

1t has been found that the aluminum alloy wire of the present inventionhas a characteristic of thermal stability which exceeds the thermalstability of other aluminum alloy wires. In order to demonstrate thisfeature a group of wires is prepared for testing decrease in tensile andyield strength in response to ageing at established temperatures andtimes. The samples have compositions and are processed as shown in thefollowing table:

TABLE ll] tion as described hereinbefore and as defined in the appendedclaims.

Sample Co Fe Al Processing No. l 0.60 0.05 Remainder Continuous castingand immediate hot rolling; drawing to flat magnet wire with nointermediate anneals and then partially annealed No. 2 0.045 RemainderBillet casting; homogenization and rolling; drawing with intermediateanneals to flat magnet wire and then partially annealed.

0.045 Remainder Billet casting; homogenization and rolling; drawing withintermediate anneals to form flat magnet wire and then partiallyannealed.

No. 4 0.80 0.60 Remainder Continuous casting and immediate hot rolling;drawing to flat magnet wire with no intermediate anneals and thenpartially annealed The results of the test are reproduced in thefollowing table:

TABLE IV 160C-AGE1NG TEMP. 190-200C AGEING TEMP. DECREASE DECREASEDECREASE SAMPLE TIME IN YS 1N UTS TlME IN YS lN UTS No. l 100 hrs. 0 100hrs. 600 psi I200 psi 500 hrs. 1,800 psi 0 670 hrs. 4,200 psi I200 psiNo. 2 100 hrs. 0 0 100 hrs. 2,700 psi 2300 psi 500 hrs. 1,800 psi 0 550hrs. 9,300 psi 5000 psi No. 3 100 hrs. 1,400 psi 0 480 hrs. 2,800 psi 0NO TEST No. 4 H hrs. 0 (l 500 hrs. (1 550 hrs. (1 0 YS Yield StrengthUTS Ultimate Tensile Strength A significant aspect shown by the resultsof these tests is the lack of thermal stability obtainable with severalaluminum alloys. The test sample wires identified as No. 2 and 3 show asignificant decrease in thermal stability in the yield and tensilestrength tests and alloy No. 2 has almost completely softened after a550 hour soak period at 190-200C. On the other hand, the wire fabricatedfrom the present alloy demonstrates a high degree of thermal stabilityby exhibiting zero decreases in yield and tensile strength.

For the purpose of clarity, the following terminology used in thisapplication is explained as follows:

Aluminum alloy rod A solid product that is long in relation to itscross-section. Rod normally has a cross-section of between three inchesand 0.375 inches.

Aluminum alloy wire A solid wrought product that is long in relation toits cross-section, which is square or rectangular with sharp or roundedcorners or edges, or is round, a regular hexagon or a regular octagon,and whose diameter or greatest perpendicular distance between parallelfaces is between 0.374 inches and 0.00- 31 inches.

While this invention has been described in detail with particularreference to preferred embodiments thereof, it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invensentially of from about 0.20 to about 1.60 weight percentcobalt, from about 0.30 to about 1.30 weight percent iron, the remainderbeing aluminum with asso ciated trace elements, said aluminum alloyelectrical conductor having the following properties when measured as aNo. 10 A.W.G. fully annealed wire:

Tensile strength: 12,000 24,000 psi Elongation: l2 30 percent Yieldstrength: 8,000 18,000 psi.

2. The aluminum alloy electrical conductor according to claim 1 furtherincluding an additional alloying element selected from the groupconsisting of magnesium, copper, silicon and mixtures thereof; thecombined weight percentage of magnesium and copper not to exceed about0.8 percent, and the silicon weight percentage not to exceed about 0.45percent.

3. The aluminum alloy electrical conductor according to claim 2 whereinthe combined weight percentage of magnesium, copper and silicon not toexceed about 0.8 percent when the combined weight percentage of cobaltand iron is 1.8 percent or greater.

4. The aluminum alloy electrical conductor according to claim 2 whereinthe combined weight percentage of magnesium and copper does not exceedabout 0.20 percent, the combined weight percentage of additionalalloying elements does not exceed about 0.10 percent,

8. The aluminum alloy electrical conductor according to claim 2 whereincobalt is present in a weight percentage of from about 0.20 to about 1.0percent and iron is present in a weight percentage of from about 0.3percent to about 1.0 percent.

9. The aluminum alloy electrical conductor according to claim 2 whereincobalt is present in a weight percentage of from about 0.30 percent toabout 0.80 percent.

10. The aluminum alloy electrical conductor according to claim 1 whereinthe weight percentages of the constitutents are as follows:

Cobalt Iron 0.50% Misch Metal 0.40% Aluminum remainder.

11. The aluminum alloy electrical conductor according to claim 1 whereinthe weight percentages ,of the constituents are as follows:

Cobalt 0.110% Iron 0.40% Niobium 0.20% Tantalum 0.2071 Aluminumremainder.

12. The aluminum alloy electrical conductor according to claim 2 whereinthe weight percentages of the constituents are as follows:

Cobalt 0.80% Iron 0.35% Copper 0.40% Silicon 0.30% Aluminum remainder.

13. The aluminum alloy electrical conductor according to claim 1 whereinthe weight percentages of the constituents are as follows:

Cobalt 0.80% Iron 0.45% Zirconium 0.30% Aluminum remainder.

14. The aluminum alloy electrical conductor according to claim 1 whereinsaid conductor is in the form of a rod.

15. The aluminum alloy electrical conductor according to claim 1 whereinsaid conductor is in the form of a wire.

16. Aluminum alloy electrical conductor having a minimum conductivity of58 percent IACS consisting essentially of from about 0.20 to about '1.60 weight percent cobalt, from about 0.30 to about 1.30 weight percentiron, the remainder being aluminum with associated trace elements, saidaluminum alloy electrical conductor having the following properties whenmeasured as a fully annealed wire:

Tensile strength: at least 12,000 psi Yield strength: at least 8,000psi.

17. The aluminum alloy electrical conductor according to claim 16further including an additional alloying element selected from the groupconsisting of magnesium, copper, silicon and mixtures thereof; thecombined weight percentage of the magnesium and copper not to exceedabout 0.8 percent, and the silicon weight percentage not to exceed about0.45 percent.

18. Method of preparing an aluminum alloy conductor having a minimumconductivity of at least 58 percent IACS comprising the steps of:

A. alloying from about 0.20 to about 1.60 weight percent cobalt withabout 0.30 to about 1.30 weight percent iron, the remainder beingaluminum with associated trace elements;

B. casting the alloy in a moving mold formed between a groove in theperiphery of a rotating casting wheel and a metal belt lying adjacentsaid groove for a portion of its length;

C. hot rolling the cast alloy substantially immediately after castingwhile the cast alloy is in substantially that condition as cast to forma continuous rod;

said aluminum alloy conductor having the following properties as a fullyannealed wire:

Tensile strength: at least 12,000 psi Yield strength: at least 8,000psi.

19. Method of preparing an aluminum alloy conductor in accordance withclaim 18 including the further step of drawing said conductor throughwire-drawing dies, without annealing the conductor between drawing dies,to form wire..

20. The method according to claim 18 wherein the alloying stepalsoincludes the addition of alloying elements selected from the groupconsisting of magnesium, copper, silicon and mixtures thereof, inamounts sufficient to yield said alloy wherein the combined weightpercentage of magnesium and copper does not exceed about 0.8 percent,and thesilicon weight percentage does not exceed about 0.45 percent.

21. The method according to claim 18 wherein the alloying step includesthe addition of magnesium, copper and silicon in amounts sufficient toyield said alloy wherein the combined weight percentage does not exceedabout 0.8 percent when the combined weight percentage of cobalt and ironis 1.8 percent or greater.

22. The method according to claim 18 wherein the alloying step includesthe addition of magnesium and copper in amounts sufficient to yield saidalloy wherein the combined weight percentage does not exceed about 0.20percent and the combined weight percentage of cobalt and iron is about2.90 percent or less.

23. The method according to claim 18 wherein the additional alloyingelement added is magnesium in an amount sufficient to yield up to about0.40 weight percent magnesium.

24. The method according to claim 18 wherein the additional alloyingelement added is copper in an amount sufficient to yield up to about0.40 weight percent copper.

25. The method according to claim 18 wherein the additional alloyingelement added is silicon in an amount sufficient to yield up to about0.45 weight percent silicon.

26. The method according to claim 18 wherein cobalt is added in anamount sufficient to yield a weight percentage of from about 0.20percent to about 1.0 percent cobalt and iron is added in an amountsufficient to yield a weight percentage of from about 0.3 percent toabout 1.0 percent iron.

27. The method according to claim 18 wherein cobalt is added in anamount sufficient to yield a weight percentage of from about 0.30percent to about 0.80 percent cobalt and iron is added in an amountsufficient to yield a weight percentage of from about 0.40 percent toabout 0.70% iron.

28. The method according to claim 18 wherein cobalt, iron and mischmetal are added in amounts sufficient to yield an alloy having thefollowing weight percentages:

Cobalt 0.80% lron 0.50% Misch metal 0.40% Aluminum remainder.

29. The method according to claim 18 wherein cobalt, iron, niobium andtantalum are added in amounts sufficient to yield an alloy having thefollowing weight percentages:

Cobalt 0.80% Iron 0.40% Niobium 0.20%

0.20% remainder.

Tantalum Aluminum 30. The method according to claim 18 wherein cobalt,iron, copper and silicon are added in amounts sufficient to yield analloy having the following weight percentages:

Cobalt 0.80% Iron 0.35% Copper 0.40% Silicon 0.30% Aluminum remainder.

31. The method according to claim 18 wherein cobalt, iron, and zirconiumare added in an amount sufficient to yield an alloy having the followingweight percentages:

Cobalt 0.80% Iron 0.45% Zirconium 0.30% Aluminum remainder.

32. The method according to claim 18 wherein said

2. The aluminum alloy electrical conductor according to claim 1 furtherincluding an additional alloying element selected from the groupconsisting of magnesium, copper, silicon and mixtures thereof; thecombined weight percentage of magnesium and copper not to exceed about0.8 percent, and the silicon weight percentage not to exceed about 0.45percent.
 3. The aluminum alloy electrical conductor according to claim 2wherein the combined weight percentage of magnesium, copper and siliconnot to exceed about 0.8 percent when the combined weight percentage ofcobalt and iron is 1.8 percent or greater.
 4. The aluminum alloyelectrical conductor according to claim 2 wherein the combined weightpercentage of magnesium and copper does not exceed about 0.20 percent,the combined weight percentage of additional alloying elements does notexceed about 0.10 percent, and the combined weight percentage of cobaltand iron is about 2.90 percent or less.
 5. The aluminum alloy electricalconductor according to claim 2 wherein the additional alloying elementis magnesium in an amount up to about 0.40 weight percent.
 6. Thealuminum alloy electrical conductor according to claim 2 wherein theadditional alloying element is copper in an amount up to about 0.40weight percent.
 7. The aluminum alloy electrical conductor according toclaim 2 wherein the additional alloying element is silicon in an amountup to about 0.45 weight percent.
 8. The aluminum alloy electricalconductor according to claim 2 wherein cobalt is present in a weightpercentage of from about 0.20 to about 1.0 percent and iron is presentin a weight percentage of from about 0.3 percent to about 1.0 percent.9. The aluminum alloy electrical conductor according to claim 2 whereincobalt is present in a weight percentage of from about 0.30 percent toabout 0.80 percent.
 10. The aluminum alloy electrical conductoraccording to claim 1 wherein the weight percentages of the constitutentsare as follows:
 11. The aluminum alloy electrical conductor according toclaim 1 wherein the weight percentages of the constituents are asfollows:
 12. The aluminum alloy electrical conductor according to claim2 wherein the weight percentages of the constituents are as follows: 13.The aluminum alloy electrical conductor according to claim 1 wherein theweight percentages of the constituents are as follows:
 14. The aluminumalloy electrical conductor according to claim 1 wherein said conductoris in the form of a rod.
 15. The aluminum alloy electrical conductoraccording to claim 1 wherein said conductor is in the form of a wire.16. Aluminum alloy electrical conductor having a minimum conductivity of58 percent IACS consisting essentially of from about 0.20 to about 1.60weight percent cobalt, from about 0.30 to about 1.30 weight percentiron, the remainder being aluminum with associated trace elements, saidaluminum alloy electrical conductor having the following properties whenmeasured as a fully annealed wire: Tensile strength: at least 12,000 psiYield strength: at least 8,000 psi.
 17. The aluminum alloy electricalconductor according to claim 16 further including an additional alloyingelement selected from the group consIsting of magnesium, copper, siliconand mixtures thereof; the combined weight percentage of the magnesiumand copper not to exceed about 0.8 percent, and the silicon weightpercentage not to exceed about 0.45 percent.
 18. Method of preparing analuminum alloy conductor having a minimum conductivity of at least 58percent IACS comprising the steps of: A. alloying from about 0.20 toabout 1.60 weight percent cobalt with about 0.30 to about 1.30 weightpercent iron, the remainder being aluminum with associated traceelements; B. casting the alloy in a moving mold formed between a groovein the periphery of a rotating casting wheel and a metal belt lyingadjacent said groove for a portion of its length; C. hot rolling thecast alloy substantially immediately after casting while the cast alloyis in substantially that condition as cast to form a continuous rod;said aluminum alloy conductor having the following properties as a fullyannealed wire: Tensile strength: at least 12,000 psi Yield strength: atleast 8,000 psi.
 19. Method of preparing an aluminum alloy conductor inaccordance with claim 18 including the further step of drawing saidconductor through wire-drawing dies, without annealing the conductorbetween drawing dies, to form wire.
 20. The method according to claim 18wherein the alloying step also includes the addition of alloyingelements selected from the group consisting of magnesium, copper,silicon and mixtures thereof, in amounts sufficient to yield said alloywherein the combined weight percentage of magnesium and copper does notexceed about 0.8 percent, and the silicon weight percentage does notexceed about 0.45 percent.
 21. The method according to claim 18 whereinthe alloying step includes the addition of magnesium, copper and siliconin amounts sufficient to yield said alloy wherein the combined weightpercentage does not exceed about 0.8 percent when the combined weightpercentage of cobalt and iron is 1.8 percent or greater.
 22. The methodaccording to claim 18 wherein the alloying step includes the addition ofmagnesium and copper in amounts sufficient to yield said alloy whereinthe combined weight percentage does not exceed about 0.20 percent andthe combined weight percentage of cobalt and iron is about 2.90 percentor less.
 23. The method according to claim 18 wherein the additionalalloying element added is magnesium in an amount sufficient to yield upto about 0.40 weight percent magnesium.
 24. The method according toclaim 18 wherein the additional alloying element added is copper in anamount sufficient to yield up to about 0.40 weight percent copper. 25.The method according to claim 18 wherein the additional alloying elementadded is silicon in an amount sufficient to yield up to about 0.45weight percent silicon.
 26. The method according to claim 18 whereincobalt is added in an amount sufficient to yield a weight percentage offrom about 0.20 percent to about 1.0 percent cobalt and iron is added inan amount sufficient to yield a weight percentage of from about 0.3percent to about 1.0 percent iron.
 27. The method according to claim 18wherein cobalt is added in an amount sufficient to yield a weightpercentage of from about 0.30 percent to about 0.80 percent cobalt andiron is added in an amount sufficient to yield a weight percentage offrom about 0.40 percent to about 0.70% iron.
 28. The method according toclaim 18 wherein cobalt, iron and misch metal are added in amountssufficient to yield an alloy having the following weight percentages:29. The method according to claim 18 wherein cobalt, iron, niobium andtantalum are added in amounts sufficient to yield an alloy having thefollowing weight percentages:
 30. The method according to claim 18wherein cobalt, iron, copper and silicon are added in amounts sufficientto yield an alloy having the following weight percentages:
 31. Themethod according to claim 18 wherein cobalt, iron, and zirconium areadded in an amount sufficient to yield an alloy having the followingweight percentages:
 32. The method according to claim 18 wherein saidalloy conductor is formed into a wire having the following propertieswhen measured as a No. 10 A.W.G. fully annealed wire: Tensile strength:12,000 - 24,000 psi Elongation: 12 - 30 percent Yield strength: 8,000 -18,000 psi.